However, British roads present a unique challenge, said Edmund King, president of the AA.

"We all want to promote fuel efficiency and reduce congestion but we are not yet convinced that lorry platooning on UK motorways is the way to go about it," he said, pointing out, for example, that small convoys of lorries can block road signs from the view of other road users.

"We have some of the busiest motorways in Europe with many more exits and entries.

"Platooning may work on the miles of deserted freeways in Arizona or Nevada but this is not America," he added.

His comments were echoed by the RAC Foundation.

Its director, Steve Gooding, said: "Streams of close-running HGVs could provide financial savings on long-distance journeys, but on our heavily congested motorways - with stop-start traffic and vehicles jostling for position - the benefits are less certain."

Campaign group the Road Haulage Association said "safety has to come first".

Transport Minister Paul Maynard said platooning could lead to cheaper fuel bills, lower emissions and less congestion.

"But first we must make sure the technology is safe and works well on our roads, and that's why we are investing in these trials," he said.